Field emission devices (FEDs) are known in the art. Such prior art devices are constructed by a variety of methods all of which yield structures with the purpose of emitting electrons from an emitter electrode. FEDs typically include an anode, a cathode, and phosphors disposed therebetween in a position corresponding to each pixel. During operation, electrons emitted by the cathode, are accelerated by an electric field created between the cathode and the anode, and impinge upon the phosphors, thereby exciting the phosphors to emit light, and thus display an image.
It is known in the prior art to form cathode structures utilizing carbon nanotube (CNT) deposition. Typically, during cathode fabrication, a binder material and CNT particles are deposited simultaneously. One means of deposition is to mix the CNT particles with the binder into a paste and deposit the paste. The binder is necessary in electrophoretic deposition (EPD) to glue the CNT particles to the substrate. As stated, generally, the deposition of the binder is performed concomitantly with the particle deposition. However, a stable colloidal suspension, which is desirable for uniform films, is not always obtainable with the binder material and the powder together in the same solution. The binder material, or binder salt, imposes a positive charge onto the suspended particles. In the case of CNT particles, this results in a failed suspension, with CNT particles clumping together. EPD from such a solution leads to highly non-uniform deposits with high density of agglomerates present on the film surface. Non-uniform EPD coatings lead to non-uniformities in the spatial distribution of field emission current and to defects in the cathodes.
Accordingly, there exists a need for an improved cathode structure and method for fabricating the cathode structure using electrophoretic deposition techniques that will result in a uniform EPD coating.
It is an object of the present invention to provide for a FED cathode and method of fabricating a FED cathode using electrophoretic deposition of carbon nanotubes.
It is another object of the present invention to provide for a FED cathode and method of fabricating an FED cathode wherein a uniform EPD coating is achieved.
It is yet another object of the present invention to provide for an EPD coating that does not require post-deposition activation to obtain a high density of emission sites.